1. Field of the Invention
This invention relates to a gas-turbine engine combustor.
2. Description of the Related Art
As taught for example by Japanese Laid-Open Patent Application No. 2000-74374, one known type of gas-turbine engine combustor comprises a combination of combustors for diffusive combustion and for premixed combustion.
Specifically, in the combustor disclosed in this prior art reference, premixing pipe has a single nozzle or jet for diffusive combustion disposed at its center and a plurality of nozzles or jets for premixed combustion are formed around the diffusive combustion nozzle and an ignition plug is disposed at a location eccentric to the center.
In a gas-turbine engine of this type, it is preferable to utilize premixed combustion in the point of improved emission performance. However, since premixed combustion is less stable than diffusive combustion, idling and other such operation conditions require diffusive combustion. Therefore, the mode of combustion is frequently switched between diffusive combustion and premixed combustion. Since the combustion is susceptible to be unstable at the time of combustion mode switching, it becomes necessary to ensure ignition performance and flame holding during the combustion mode switching.
However, as mentioned above, since the prior art combustor is configured in such a way that the premixing pipe has a single nozzle or jet for diffusive combustion disposed at its center and a plurality of nozzles or jets for premixed combustion are formed around the diffusive combustion nozzle and an ignition plug is disposed at a location eccentric to the center, it is not always satisfactory in the viewpoint of ignition performance and flame holding and leaves much to be desired from the aspect of stabilization of diffusive combustion, expansion of range over which premix combustion is possible and enhancing of combustion stability and the like at the time of switching between premixed combustion and diffusive combustion.
An object of the present invention is therefore to overcome the foregoing shortcomings by providing a gas-turbine engine combustor that enables to enhance ignition performance and flame holding and to expand the range over which premixed combustion is possible, while enhancing combustion stability and the like at the time of switching between premixed combustion and diffusive combustion.
The present invention achieves the foregoing object by providing a gas-turbine engine combustor having a plurality of venturi mixers, each connected to an air supply path that passes air compressed by a compressor and to a supply source of gaseous fuel, which mix the air and the gaseous fuel to produce an air-fuel mixture and supply the air-fuel mixture to a combustion chamber for generating premixed combustion or diffusive combustion such that produced combustion gas rotates a turbine that outputs its rotation through an output shaft, while driving the compressor by the rotation; comprising: an air inlet formed in each of the venturi mixers and connecting to the air supply path; a fuel inlet formed in each of the venturi mixers and connecting to the supply source of gaseous fuel; an air-fuel mixture generating passage, formed in each of the venturi mixtures, which connects to the air inlet and the fuel inlet and merges with an air-fuel mixture generating section to produce the air-fuel mixture; a first nozzle or jet which opens into the combustion chamber at an end of the air-fuel mixture generating passage; an ignition plug installed on a center axis of the combustion chamber which ignites the air-fuel mixture and has a body and a heating element at its tip; a second fuel passage for diffusive combustion which is formed around the body of ignition plug and is connected to the supply of gaseous fuel; and a plurality of second nozzles or jets which are located around the heating element of the ignition plug and open into the combustion chamber at an end of the second fuel passage.